Transcript 16-WHITE MATTER

BY
PROF.
SAEED ABUEL MAKAREM
• Each cerebral hemisphere
consists of:
• 1- Cerebral cortex:
(outer layer of grey matter).
• 2-White matter:
(enormous mass of nerve
fibers).
• 3-Basal ganglia:
(collection of grey matter in
the white matter).
• 4-Lateral ventricle:
• The cavity of the
hemisphere.
White matter of Cerebrum
• There are 3 types:
• 1- Association fibers:
• Interconnect cortical sites lying
within one hemisphere.
• They are short or long fibers .
• 2- Commissural fibers:
• Connecting functionally related
gyri on both hemisphere.
• 3- Projection fibers:
• Connecting the cortex with the
lower centers in thalamus brain
stem, or spinal cord.
• They are ascending or
descending.
WHITE MATTER OF
CEREBRAL HEMISPHERE
• A- Short association fibers:
• Connect nearer gyri on the same
hemisphere.
• B- Long association fibers:
• Connect distant gyri on the same
hemisphere.
• Example:
• 1-Superior longitudinal fasciculus:
• Connects the frontal & occipital
lobes.
• It lies above the insula.
• It has a subsidiary bundle known as
arcuate fasciculus, which connects
the frontal & temporal lobes.
• It is important for language
function
Association fibers
• 2- Inferior longitudinal
fasciculus:
• Connects the occipital &
temporal poles.
• It is contributed in visual
recognition.
• 3- Uncinate fasciculus:
• U-shaped curved around
the bottom of the lateral
sulcus.
• It connects the anterior &
inferior parts of the frontal
gyrus with the temporal
gyri.
• It is important for
behavioral regulation.
Association fibers
• 4- Cingulum:
• Begins in the anterior
perforated substance in
the frontal lobe.
• Runs in cingulate gyrus.
• Curves inferiorly to run
in the Parahippocampal
gyrus.
• It is a part of the limbic
system
• It terminates in the
Uncus.
Association fibers
COMMISSURAL FIBERS
• The major commissural
fibers are:
• 1-Corps callosum.
• 2-Anterior commissure.
• 3-Hippocampal
commissure ( Commissure
of the fornix).
CORPUS CALLOSUM
• The greatest commissure of
brain.
• It connects homologous
areas of the 2 hemispheres
• Formed of 4 parts: Rostrum,
genu, body & splenium.
• Lies in floor of great
longitudinal fissure .
• Its inferior surface is
attached to fornix by the
septum pellucidum.
• Rostrum & genu interconnect
the anterior part of the
frontal lobe.
• The trunk interconnects the
posterior part of the frontal
& parietal & temporal lobes.
• The splenium interconnects
the occipital lobes.
• The fibers of the rostrum &
genu arch forward to form
forceps minor.
• The fibers of splenium arch
backward to form forceps
major.
CORPUS CALLOSUM
ANTERIOR COMISSURE
• Rounded commissure.
• Lies behind the
lamina terminals.
• Runs transversely in
front of the anterior
column of fornix.
• Interconnects the
middle & inferior
temporal gyri.
• Also, it connects the
olfactory regions of
the 2 hemisphere.
HIPPOCAMPAL COMMISSURE
• Composed of transverse fibers .
• Interconnects the posterior columns of the fornix.
• These are fibers which
connect the cortex to other
areas in the brain stem &
the spinal cord.
• Projection fibers are 2
types:
• A- Ascending (afferent),or
corticopetal:
• Conveying fibers to the
cortex
• 1- Thalamic radiation:
connecting different
thalamic nuclei with
different parts of cortex.
• 2- Optic radiation.
• 3- Auditory radiation.
PROJECTION FIBERS
• B- Descending (Efferent), or
corticofugal:
• 1. Pyramidal:
a. Corticospinal.
b. Corticobulbar.
• 2. Corticopontine.
• 3. Corticoreticular.
• 4. Corticorubral
PROJECTION FIBERS
• Thick band of
projection fibers.
• V-shaped with its
concavity directed
laterally in horizontal
section
• Its concavity is
related to Lentiform
nucleus.
• It is formed of:
• Anterior limb.
• Genu.
• Posterior limb.
INTERNAL CAPSULE
• Anterior limb:
• Between head of caudate
nucleus & lentiform nucleus.
• It contains:
• 1-Anterior thalamic
radiation:
From anterior & mediodorsal
thalamic nuclei, to the frontal
cortex.
• 2-Frontopontine fibers:
That project to pontine nuclei,
in the basal part of the Pons.
INTERNAL CAPSULE
• Genu of internal capsule:
• Is the angle of the V which
points medially, between
head of caudate nucleus
and thalamus.
• It contains:
• 1- Corticonuclear
(Corticobulbar).
• 2- Anterior part of sensory
(superior thalamic)
radiation, from ventral
anterior & ventral lateral
nuclei to motor regions of
the frontal lobe.
INTERNAL CAPSULE
• Posterior limb:
• A-Lenticothalamic part
• Lies between thalamus &
lentiform nucleus.
• Contains:
• 1-Corticospinal fibers.
• 2-Frontopontine.
• 3-Frontorubral.
• 4-Great part of sensory
(superior thalamic )
radiation, from the ventral
posterior nucleus to the
primary somatosensory
cortex.
INTERNAL CAPSULE
• B-Retrolentiular
part:
• It contains fibers from
medial & lateral
geniculate nuclei of
thalamus, which form the
auditory & optic radiation.
• Optic radiation passes to
visual cortex, around the
calcarine sulcus
(geniculoalcarine fibers).
• Auditory radiation passes
to superior temporal
gyrus.
INTERNAL CAPSULE